Examples of methods that may be used for printing images such as text, pictures or designs onto fabrics such as woven fabrics and nonwoven fabrics include not only screen printing methods and roller printing methods, but more recently inkjet printing methods, in which image processing is conducted using a computer and the image can then be printed without a plate or screen, which are attracting considerable attention.
Inkjet printing methods include transfer methods in which following printing onto a transfer sheet, the image is transferred to the fabric by thermal transfer, iron printing methods in which following printing to a heat-fixable resin film (an iron printing sheet), the resin film is subjected to heat fixing, and direct printing methods in which printing is conducted directly onto the fabric.
Of these methods, direct printing methods, which require no secondary materials such as the transfer sheet required in transfer methods, and which suffer no deterioration in texture such as that produced by iron printing methods, are attracting much attention.
In the case of direct printing methods, for reasons including the fact that inkjet recording inks are of low viscosity and penetrate readily, the fact that the hiding power is inferior in the case of pigment inks due to the small pigment particle size (generally not more than 300 nm), and the fact that the amount of ink applied is small, the image of a printed item tends to be affected by the base color of the fabric, and printing onto dark-colored fabrics such as black or navy blue fabrics has proven problematic.
In order to address this issue, discharge-type direct inkjet printing methods are being developed in which a discharge ink is printed onto the fabric prior to printing, and the desired color ink printing is then performed. However, because the state of the discharge varies depending on the type of fabric, quality stability is problematic. Moreover, completely removing the dye from the fabric is difficult, meaning obtaining vivid coloration is problematic.
Another issue that is unique to printing onto fibrous products is the requirement that images printed onto fabrics used for clothing or the like must exhibit high levels of durability to washing and friction.
In those cases where a pigment is used as the colorant, advantages include a high degree of lightfastness, favorable compatibility with a plurality of fiber types and the fact that a colorant removal step is unnecessary, and the simplicity provided by pigments is very attractive. In order to fix the pigment, a binder component must be added to the ink. However, in the case of an inkjet ink, from the viewpoints of the discharge stability, and the discharge properties and degree of nozzle blocking following sitting within the head, a large amount of the binder component cannot be used, and therefore the durability relative to washing and friction tends to be unsatisfactory.
Japanese Patent Laid-Open No. 2005-161583 discloses a method in which a plurality of printing layers are superimposed on a fabric, wherein temporary heat fixing is conducted at least once during the superimposition of the plurality of printing layers, and a main heat fixing operation is conducted following completion of the final printing operation. This method has an object of imparting superior washing durability, and obtaining a white inkjet image of superior visibility on a dark-colored fabric. However, because of the significant increase in the number of steps required by the plurality of printing operations and the heat fixing and the like, this method still has problems in terms of productivity.
Japanese Patent Laid-Open No. S61-215787 discloses an inkjet recording method that uses two liquids, wherein a reaction liquid comprising a polyvalent metal salt, and an ink composition comprising a pigment and a resin emulsion are printed and adhered to a recording medium. It is disclosed that this method enables printing bleeding and printing irregularities to be suppressed, and effectively prevents color bleeding. However, this method displays inadequate hiding power for printing onto dark-colored fabrics, and further improvements are also required in the durability to washing and friction.